As a semiconductor module, there is known a device in which a semiconductor element used for an electrical power converter is sealed with resin and modularized. In this sort of semiconductor module, a chip arrangement surface of a ceramic substrate is sealed with resin, and heat is radiated from a back surface of the ceramic substrate. For this reason, if, due to a difference in a thermal expansion coefficient between the ceramic substrate and the resin, mold shrinkage of the resin, or warpage of the substrate caused by a heat cycle during operation occurs, the occurrence causes a reduction in radiation efficiency, or peeling-off of a semiconductor chip.
Because of this, in a typical semiconductor module, a ceramic substrate on which chip parts including a semiconductor chip are soldered is bonded onto a thick metal plate such as a copper (Cu) or iron (Fe) plate through a heat spreader or an insulating sheet. Also, a case for surrounding a chip mounting surface of the ceramic substrate is attached, into which silicon gel is injected to protect the chip parts, and then resin is further filled.
However, in the case where the silicone gel is used to protect the chip parts, moisture intruding from a gap of the case may adversely influence the chip parts. Also, electrical connections among the chip parts are made with wire bonding, soldering of a lead frame, or ultrasonic bonding; however, if a part of the bonding is deteriorated by heat or the like, the use of the silicone gel as a protecting material makes it difficult to stably fix the wire or lead frame.
For this reason, there has been proposed a semiconductor module in which resin is directly filled on a chip mounting surface of a ceramic substrate without use of the protecting material such as silicone gel (e.g., Patent document 1). In Patent document 1, the ceramic substrate is joined onto a metal plate to form a module substrate on which a semiconductor chip is mounted, and then the resin is injected into a space surrounded by an enclosing case, a frame body, and a module substrate. If the enclosing case has sufficient stiffness, stress due to mold shrinkage upon curing of the sealing resin can be dispersed into the module substrate and the frame body to prevent warpage of the module substrate, and therefore temperature cycle resistance can be improved.
Patent document 1; Japanese Unexamined Patent Publication No. 1997-237869